diff --git a/src/SES.hs b/src/SES.hs
index 4d3eedfc8..b8875a71d 100644
--- a/src/SES.hs
+++ b/src/SES.hs
@@ -11,8 +11,13 @@ ses :: Compare a -> [Term a Info] -> [Term a Info] -> [Diff a]
 ses _ [] b = (Pure . Insert) <$> b
 ses _ a [] = (Pure . Delete) <$> a
 ses recur (a : as) (b : bs) = case recur a b of
-  Just f -> f : ses recur as bs
-  Nothing -> if SES.cost delete < SES.cost insert then delete else insert where
+  Just f | SES.cost delete < SES.cost insert && SES.cost delete < SES.cost copy -> delete
+         | SES.cost insert < SES.cost copy -> insert
+         | otherwise -> copy
+    where
+      copy = f : ses recur as bs
+  Nothing -> if SES.cost delete < SES.cost insert then delete else insert
+  where
     delete = (Pure . Delete $ a) : ses recur as (b : bs)
     insert = (Pure . Insert $ b) : ses recur (a : as) bs